In tubers, such as onion plants, the edible part of the plant is the bulbous lower portion while a leafy top extends above the bulb. An acre of commercial onions can contain between 80,000 and 150,000 plants, with each bulb weighing between 1/2 to 2 lbs., and with the green leafy top or stalk portion weighing almost as much as the bulb. Upon reaching maturity, the stalks of the onions wither and fall onto the ground. The bent stalks lie all over the ground and hinder visibility of, and ready access to, the ripe bulbs. The harvesting process is complicated by the matted covering of the onion tops on the ground.
Currently, onions are uprooted by a breaker bar which is pulled through the ground below the onions to thrust the onions out of the ground. After drying for a few days, the uprooted onions are manually topped by grabbing the onion stalks and using scissors to cut off the tops, after which the onions are mechanically or manually gathered, and taken to a facility for packing or storage.
In some cases, the uprooted, untopped onions are mechanically gathered and taken to a packing area where the onions are again manually topped with scissors or clippers. All onion residues are discarded at this stage if they have not been eliminated earlier. Because the onion tops are acidic, the disposal of large quantities of onion tops gathered at the packing facilities becomes a great environmental concern, with attendant difficulties in environmentally safe disposal of large quantities of tops.
As the onion crop becomes ripe and ready for harvesting at about the same time in a given geographical region, large numbers of workers must be employed to accomplish the manual topping task. This manual labor is very expensive, and creates significant uncertainties in arranging and coordinating sufficient numbers of workers, if they are even available when needed.
Several patents disclose equipment to top onions and tubers. The most recent development is disclosed in U.S. Pat. No 5,107,664, entitled "VEGETABLE TOPPER" owned by the same entity as the current invention. The machine raises and cuts the tops off of tubers in two adjacent rows and consolidates the topped tubers into one row. Disadvantageously, the means used to raise the tops is a large vacuum hood located a few inches off of the ground which also suctions an appreciable amount of topsoil along with the onion tops, creating a large dust cloud which can prove unacceptable. The nature of the vacuum force underneath the hood varies quite a bit depending on the terrain and disposition of the onions in the ground.
Patents to Davis (U.S. Pat. No. 1,347,733) and Sampson (U.S. Pat. No. 2,579,013) both disclose a machine for raising and cutting potato-vines and the like, and onions, respectively. A disadvantage of both devices is that only a small area below the fans can be harvested. Another disadvantage is the distribution of whole, severed vines back onto the field, covering the crops on adjacent rows which then are difficult to locate and harvest.
U.S. Pat. No. 4,757,670, issued to Kinch, describes an agricultural crop defoliator which uses a blowing technique to elevate the tops of plants for cutting. Soviet Union Patent No. 3840-660-A, issued to Vege, discloses a stem cutter for trimming onion haulms (stalks). Rotating elastic rods lift the tops of the plants to come in contact with rotating blades inside a drum.
The harvesting equipment described in the above-mentioned patents share the common disadvantage of being cumbersome to maneuver around sharp corners, requiring large areas at the ends of the fields to allow the devices to be turned. U.S. Pat. No. 5,107,664 discloses steerable rear wheels, yet the distance from the rear wheels to the tractor wheels is around 18 feet, requiring a substantial space at the end of each row to turn. Sampson, Kinch and Vege show simple towed devices which restrict the arc of turn to that which avoids jack-knifing or collision between the towing and towed vehicles. Davis allows for steering wheels on the front which would limit the arc of turn to that allowed by the wheel base of the device. There is thus a need for a device with steering that enables sharp corners to be made, so that more crops can be planted in the fields.
Whatever the claimed advantages of the prior equipment, the current widespread use of inefficient and costly manual labor demonstrates that these prior inventions did not succeed. While U.S. Pat. No. 5,107,664 cures many of these problems, it fails to address the significant problem of dust clouds and unsteady vacuum force. There thus exists a need for a mechanical topper that addresses the above needs, and overcomes the drawbacks of prior vegetable topping machines by increasing the harvesting efficiency without damaging the tubers or bulbs.